Probe resistance measurement method and semiconductor device with pads for probe resistance measurement

ABSTRACT

A probe resistance measuring method includes measuring first resistances at three or more nodes by making contact at least a part of a plurality of probes of a probe unit with three or more pads for resistance measurement based on a first correspondence relation. The measured resistances are stored as a first measurement result and contact resistances of the plurality of probes of the probe unit are calculated based on the first measurement result.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

Japan Priority Application 2007-099090, filed Apr. 5, 2007 including thespecification, drawings, claims and abstract, is incorporated herein byreference in its entirety. Japan Priority Application 2008-065625, filedMar. 14, 2008 including the specification, drawings, claims andabstract, is incorporated herein by reference in its entirety. Thisapplication is a Continuation of U.S. application Ser. No. 12/078,781,filed Apr. 4, 2008, incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Description of Related Art

In order to evaluate the electric characteristics of a device, a methodof making probes contact pads to measure a resistance between wiringlines is carried out. At this time, a contact resistance of the probeinfluences the measurement resistance. With influence of the probecontact resistance on an automatic measuring apparatus, even if anunnecessary resistance is added to the probe in the form ofcontamination to shift the electric characteristics a little bit, themeasurement value falls within a manufacturing deviation and any problemis not caused.

However, recently, it is required to reduce the deviation with the finerprocessing. Accordingly, it is impossible to meet the measurementrequisition only by an open/short check and a rough check of resistancebetween pads.

In an LSI with a high performance, recently, a sort process using notvoltage but current is performed in the sort process in which a test ofa MOSFET for characteristic monitor provided onto a product wafer iscarried out. In this sort process, the sort is performed based on athreshold voltage Vth of the MOSFET but an ON current of the MOSFET. Thethreshold voltage sort is performed by measuring a small current in theorder of microampere but the ON current sort is performed by measuring acurrent in the order of milliampere which is relatively large.Therefore, when a contact resistance of about 10Ω is attached to theprobe, a voltage drop due to the contact resistance cannot be ignored,because the current reduces at a considerable rate. Thus, the sort isinfluenced based on the contact resistance. Also, in order to meet thestrict sort rule, the measurement deviation cannot be ignored.Therefore, it is necessary to always keep the contact resistance of theprobe to a low resistance. Ideally, the contact resistance of each probemust be kept to be equal to or less than 1Ω. Thus, a technique ofmeasuring the contact resistance of the probe is demanded. Especially,the technique that can measure contact resistances of n (n≧3) probes isdemanded.

In conjunction with the above description, a method of measuring acontact resistance of a probe is described in Japanese PatentApplication Publication (JP-P2004-85377A: first related art). In thismeasuring method, a plurality of electrode pads connected with a wiringline is provided for a semiconductor device for an electric test to becarried out about. In this method of measuring a contact resistance, acurrent is supplied to the probe and a voltage is measured. Thus, thecontact resistances of the whole probes are determined from the suppliedcurrents and the measured voltages. Also, in a technique described inthis first related art, it is not possible to measure the contactresistance of each probe precisely.

Japanese Patent Application Publication (JP-P2001-343426A: secondrelated art) discloses a method of testing a semiconductor device. Inthis method, an impedance in a current path between two pads to whichtwo probes are made contact is measured, and when the measured value islarger than a predetermined value, the probe is cleaned. However, inthis method, the contact resistances of all the probes are not measuredand cannot be determined.

Also, Japanese Patent Application Publication (JP-A-Heisei 8-82657:third related art) discloses a method of testing an integrated circuitdevice. In this method, a contact state of probes with a first padsection and a second pad section is detected. The first pad section iscomposed of a plurality of electrodes and the second pad section iscomposed of a plurality of electrodes having different resistances. Inthis technique, a resistance between two pads, a contact state andneedle pressure can be detected, but the contact resistance of eachprobe cannot be determined precisely.

Also, Japanese Patent Application Publication (JP-A-Heisei 11-39898:fourth related art) discloses a semiconductor device. In this technique,a contact state of a probe group can be checked but the contactresistance of each probe cannot be determined precisely.

Also, Japanese Patent Application Publication (JP-P2004-119774A: fifthrelated art) discloses a semiconductor device. In this technique, asignal is given from a switching element so as to supply a voltage to anexternal connection pad. At this time, a contact check result to a padis outputted based on a voltage appearing on a monitor pad.

Also, Japanese Patent Application Publication (JP-P2006-59895A: sixthrelated art) discloses a method of checking a conduciveness of a contactplug or via-plug. Many checking pads are arranged and the check isperformed by using these pads.

SUMMARY

In a first aspect of the present invention, a probe resistance measuringmethod includes measuring first resistances at three or more nodes bymaking contact at least a part of a plurality of probes of a probe unitwith three or more pads for resistance measurement based on a firstcorrespondence relation; storing the measured first resistances as afirst measurement result; and calculating contact resistances of theplurality of probes of the probe unit based on the first measurementresult.

In a second aspect of the present invention, a semiconductor device withpads for probe resistance measurement, includes three or more padselectrically isolated from a semiconductor circuit formed on asemiconductor substrate; and wiring lines provided to connect betweenthe pads in series and having a same resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the presentinvention will be more apparent from the following description ofcertain preferred embodiments taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram showing a measuring method in a related art;

FIG. 2 is a diagram showing a measuring method in another related art;

FIG. 3 is a diagram showing another related art;

FIG. 4 is a diagram showing another related art;

FIGS. 5A and 5B are diagrams showing another related art;

FIGS. 6A to 6C are diagrams showing another related art;

FIG. 7A is a diagram showing a probe unit having n (n≧3) probes in thepresent invention;

FIG. 7B is a diagram showing a TEG for contact resistance measurement incase of the probe unit of three probes;

FIGS. 8A and 8B are diagrams showing a method of measuring the contactresistance of the probes while rotating a wafer;

FIG. 9 shows an example of pads which are not arranged on a straightline;

FIG. 10A is a diagram showing a TEG for contact resistance measurementcontaining three or more pads connected in series;

FIGS. 10B-1 and 10B-2 are diagrams showing a method of measuring contactresistances of probes of a probe unit by using a TEG with three or morepads connected in series;

FIGS. 11A and 11B are diagrams showing the method of measuring thecontact resistance of each probe of the probe unit of 24 probes by usinga TEG for contact resistance measurement of three pads connected inseries;

FIGS. 12A and 12B are diagrams showing a pad for resistance measurementas a linear wiring line pattern;

FIG. 13 is a diagram showing a method of measuring the contactresistance of each probe of the probe unit of many probes by using alarge area pad for resistance measurement;

FIG. 14 is a diagram showing a layout of a product chip to which the TEGwith a TEG for contact resistance measurement is applied;

FIG. 15A is a diagram showing a structure example to measure the contactresistance of a probe, by using an unused area such as a peripheralportion of a product;

FIG. 15B is a diagram showing another structure example to measure thecontact resistance of a probe, by using an unused area such as aperipheral portion of a product;

FIG. 16A is a diagram showing a structure in which the TEG for contactresistance measurement is formed not to overlap with a lower layerpattern area in a height direction;

FIG. 16B is a diagram showing a structure in which the TEG for contactresistance measurement is formed to overlap with the lower layer patternarea in the height direction;

FIG. 16C is a diagram showing a conductive pattern containing a part ofthe TEG for contact resistance measurement and a lower layer pattern asa part of a lower layer pattern area;

FIGS. 17A and 17B are schematic diagrams showing lower and upperportions in an exposure field when an exposure process is performed byusing a reduced projection type exposure apparatus, respectively;

FIG. 17C is a diagram showing the TEG for contact resistance measurementformed in a boundary of adjacent exposure fields;

FIGS. 17D and 17E are diagrams showing exposure field upper and lowerportions in the TEG for contact resistance measurement, respectively;

FIG. 17F is a diagram showing the TEG for contact resistance measurementformed in the boundary of adjacent exposure fields; and

FIG. 18 is a diagram showing the TEG for contact resistance measurementformed on scribe line areas in horizontal and vertical directions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a probe resistance measurement method and a semiconductordevice of embodiments of the present invention will be described indetail with reference to the attached drawings.

First Embodiment

FIG. 7A is a diagram showing a probe unit having n (n≧3) probes. Asshown in FIG. 7A, m (m≧3, and it is not necessary to be n=m) padsconnected in series are provided for the probe unit having the n probes.A test element group (hereinafter, to be referred to as a TEG) 20 forcontact resistance measurement is arranged in which resistances betweenthe pads 2 (resistances of wiring lines 3) are equal to each other. Thecontact resistance of each of the n probes 1 is measured by the probeunit and the pads 2. The measured contact resistance contains theresistance of a resistor from the tip of probe 1 to a wiring line of adevice through the probe unit.

(a) Case of n≧4 and n≦m

Numbers 1, 2, 3 . . . are allocated to the pads 2 in order from the pad2 arranged at the end of the TEG 20 for contact resistance measurement.First, the four pads 2 connected in series and having the numbers 1 to 4are selected. The measured resistances between No. 1 and No. 2, betweenNo. 2 and No. 3, between No. 1 and No. 3, between No. 3 and No. 4, andbetween No. 2 and No. 4 are supposed to be R12, R23, R13, R34, R24,respectively. Also, the contact resistances of the four probes 1 to thepads 2 assigned with Nos. 1, 2, 3, and 4 are supposed to be Rc1, Rc2,Rc3, and Rc4, respectively.

For example, it is supposed that the probes 1 and the pads 2 arearranged at a same pitch. Also, supposing that the wiring resistancebetween the adjacent pads 2 is r (which is constant), the followingrelation is satisfied:R12=Rc1+Rc2+rR23=Rc2+Rc3+rR13=Rc1+Rc3+2rR34=Rc3+Rc4+rR24=Rc2+Rc4+2r

Solving these equations about Rc1 to Rc4, the following relations arecalculated:Rc1=(2R12−R23+R34−R24)/2Rc2=(R12+R23−R13)/2Rc3=(R23+R34−R24)/2Rc4=(2R34−R23+R12−R13)/2

Thus, the contact resistance of each of four probes 1 is obtained.

In this way, by measuring the resistances between four pads 2 connectedin series, the contact resistances of the four probes 1 which arerespectively made contact with the four pads 2 are measured. In the sameway, the contact resistances of the n probes 1 can be measured bymeasuring the resistances between the four pads 2 in order over the nprobes 1. In a layout shown in FIG. 7A, by measuring the resistancesbetween the four pads, the contact resistances of all the n probes 1 aredetermined.

(b) Case of n>4 and m=4

An example will be described in which the contact resistances of the nprobes 1 of the probe unit are measured by using the TEG 20 for contactresistance measurement composed of four pads 2 connected in series. Atthis time, it is supposed that each of a plurality of sets of fourprobes of the n probes 1 of the probe unit is arranged to be madecontact with the four pads 2.

By measuring the resistances between the four pads 2 connected inseries, the contact resistances of the four probes 1 of each set whichare respectively made contact with the four pads are measured. Thisoperation is same as the above-mentioned first example (a).

Next, by making the four probes 1 of another set contact with the fourpads 2 connected in series, the contact resistances of the four probes 1of the other set are measured. This operation is repeated such that thefour probes 1 of each set are made contact with the four pads 2. Thus,the contact resistances of all the n probes 1 can be measured.

It should be noted that as one example of (a) case of n≧4 and n≦m and(b) case of n>4 and m=4, the embodiments have been described in whichthe contact resistances of the n probes are measured by repeating theabove operation for every four probes 1. However, the value of m is not4 but may be 5 or more. That is, the five or more proves of every setmay be respectively made contact with the five or more pads 2. In thiscase, the contact resistances of the n probes 1 can be calculated bysolving the measured resistances between pads 2 about the contactresistances.

The above contact resistance is calculated under the assumption that thewiring resistance r between adjacent pads 2 is a constant value r.However, actually, an error of the wiring resistance from the constantvalue is expected to be present. Supposing that the differences of thewiring resistances between pads 2 of the numbers 1 and 2, between pads 2of the numbers 2 and 3, between pads 2 of the numbers 3 and 4 from theconstant value r are αr, βr, and γr, respectively, the followingequations are met.R12=Rc1+Rc2+(1+α)rR23=Rc2+Rc3+(1+β)rR13=Rc1+Rc3+(2+α+β)rR34=Rc3+Rc4+(1+γ)rR24=Rc2+Rc4+(2+β+γ)r

Solving these equations about Rc1 to Rc4, the following solutions areobtained:Rc1=(R12−R23+R13)/2−r·αrRc2=(R12+R23−R13)/2Rc3=(R23+R34−R24)/2Rc4=(R34−R23+R24)/2−r·γr

That is, Rc2 and Rc3 are not affected by the errors of wiringresistances r, and the wiring resistance differences of −αr and −γr areadded to Rc1 and Rc4, respectively. For example, supposing that r<1Ω(α≈10%, γ≈10%), and about 10% of deviation is generated as a whole inthe width, length, film thickness and material resistivity of the wiringline, the wiring resistance difference added to Rc1 or Rc4 is about 0.1Ωor less. In actual, since the width and length of the wiring linebetween adjacent pads 2 are a few of tens micrometers which issufficiently long and it is possible to set a distance between the pads1 to 4 to a few of hundreds micrometers at most, there is no case thatthe wiring resistance has a large deviation of 10%, including dependencyon the film thickness and the resistivity. Accordingly, when the contactresistance is made equal to or less than 1Ω, it is possible to assumethat r is constant, since r because it is possible to ignore thedeviation of r.

(c) Case of n=3 and m=3

In case of the probe unit composed of three probes 1 (n=3), the contactresistance is measured by a method different from the above. A terminalfor a chip substrate is used. As shown in FIG. 7B, by using the TEG 20for contact resistance measurement composed of three pads 2 connected inseries and one pad 2 (pad 2 with No. 3) connected with the chipsubstrate (shown with SUB), the contact resistances of all of the threeprobes 1 can be measured. Supposing that Rs is the contact resistance ofthe terminal for the chip substrate, rs is an internal resistancebetween the pad 2 with No. 3 and the chip substrate, and R1 s, R2 s andR3 s are measured resistance between the terminal for the chip substrateand the pads 2 with Nos. 1, 2, 3, respectively, the following equationsare established:R12=Rc1+Rc2+rR23=Rc2+Rc3+rR13=Rc1+Rc3+2rR3s=Rc3+Rs+rsR2s=Rc2+Rs+r+rsR1s=Rc1+Rs+2r+rs

Solving these equations with respect to Rc1, Rc2, and Rc3, the followingcontact resistances are obtained:Rc1=(2R12−R23+R3s−R2s)/2Rc2=(R12+R23−R13)/2Rc3=(R23+R3s−R2s)/2(d) Case of n>3 and m=3

In the above (c), the embodiment is shown in which the contactresistances of the three probes 1 (n=3) of the probe unit are measured.However, if the TEG 20 for contact resistance measurement is used whichis composed of the above-mentioned three pads 2 connected in series andone pad 2 connected with the chip substrate, the contact resistances ofall the n (n>3) probes 1 of the probe unit can be measured without beinglimited to the three probes 1. In this case, it is assumed that theprobe unit has the n probes 1 for the contact resistance to be measuredand the n probes are arranged for every three probes 1 which arerespectively made contact with the three pads 1 connected in series.That is, the sets of the 3 probes 1 are sequentially made contact withthe three pads of the TEG 20 connected in series to measure the contactresistances of the probes 1. Thus, the contact resistances of the nprobes 1 can be measured.

As shown in the cases (a), (b), (c), and (d), the contact resistances ofthe three or more probes can be measured by using the TEG 20 for contactresistance measurement laid out in such a manner that the resistancesbetween the adjacent pads (the resistances of the wiring line 3) areequal, and having three or more pads connected in series. By repeatingmeasurement in order, the contact resistances of all the n probes 1 canbe measured.

In this case, it is desirable that the wiring line 3 is formed of amaterial having a low resistance such as aluminum. Also, the width,length, film thickness and the resistivity of the material of the wiringline are selected for the wiring resistances between the adjacent pads 2to be equal to each other. Specifically, it is desirable to select thewidth, length, film thickness and resistivity of the material of thewiring line such that the resistance is less than a few ohms. If thewiring resistances between the adjacent pads 2 are equal to each other,the width, length, film thickness and resistivity of material of thewiring line 3 may be different. Also, the wiring line 3 may be formed ofa combination of a plurality of wiring materials.

The contact resistance of probe 1 in this case contains the resistancefrom the inside of the probe unit to the tip of probe 1 and theresistance of the wiring line of a semiconductor chip to be measured.

It is possible to calculate the contact resistance based on thealgorithm of the auto control system immediately after the measurement.That is, in the example of FIG. 7A, numbers of 1, 2, . . . are assignedto the pads 2 from the pad 2 located at the end of the TEG 20 forcontact resistance measurement. With respect to the pads 2 with Nos. 1to 4 connected in series, the resistances R12, R23, R13, R34, and R24between the pad 2 with No. 1 and the pad 2 with No. 2, between the pad 2with No. 2 and the pad 2 with No. 3, between the pad 2 with No. 3 andthe pad 2 with No. 4, and between the pad 2 with No. 3 and the pad 2with No. 4 are measured, and the contact resistances Rc1, Rc2, Rc3, andRc4 of the probes 1 are calculated from the measured resistances inaccordance with correspondence relation of the pads 2 and the probes 1.In the same manner, the resistances of a next set of the four probes 1are measured and the contact resistances are calculated from themeasured resistances in accordance with correspondence relation of thepads 2 and the probes 1. Thus, the contact resistances of all thenprobes 1 are calculated. A process can be automatically executed ofcomparing the calculated contact resistance with a predeterminedreference and determining whether or not each probe 1 is in a goodstate. Moreover, it is possible to automatically distinguish the probethat is determined to be not in the good state in order to perform acleaning and maintenance operation to the probes 1.

Second Embodiment

As shown in FIGS. 8A and 8B, it is possible to measure the contactresistances of the probes while rotating a wafer by 180 degrees. Asshown in FIG. 8A, the TEG composed of n pads (n is an even number) isused in this embodiment. The TEG is composed of a TEG 20 for contactresistance measurement of the n/2 pads 2 from the one end and a TEG 21for device characteristic evaluation of the n/2 pads from the other end.The structure of the TEG 20 for contact resistance measurement is sameas that of the TEG shown in FIG. 7A.

First, n/2 of the n probes 1 are made contact with the TEG 20 forcontact resistance measurement, and the contact resistances are measuredby the method of described in the first embodiment. After that, by usingthe characteristic of an auto-prober, the wafer is rotated by 180degrees and the remaining n/2 probes 1 are made contact with the TEG 20for contact resistance measurement to measure the contact resistances.The contact resistances of all of the n probes 1 are measured throughtwo steps by this method.

According to the second embodiment, the number of the pads 2 for thecontact resistances to be measure can be reduced to a half of the probes1, i.e., n/2. Therefore, the pads for the device electric characteristicevaluation can be arranged in the area left with the reduction of thenumber of pads. In other words, it is possible to attempt an effectiveutilization of the layout area.

Third Embodiment

As shown in FIG. 9, it is not necessary to arrange the pads 2 on astraight line and the pads 2 may be arranged on a curved line. By layingout the pads such that the resistances between adjacent pads 2 are equalto each other, the contact resistances of probes 1 can be measured, asin FIG. 7A.

Fourth Embodiment

In this embodiment, the contact resistances are measured by use of a TEG20 for contact resistance measurement composed of three or more pads 2connected in series, as shown in FIG. 10A. As shown in FIGS. 10B-1 and10B-2, the TEGs 20 for contact resistance measurement composed of threeor more pads 2 connected in series and arranged in spaces between thepads for device electric characteristic evaluation. The contactresistance measurement of the probes 1 becomes possible by shifting theprobes 1 to the wafer with the TEG composed of the TEG 20 for contactresistance measurement, or by rotating the wafer, and making the probes1 contact the pads 2. When the probes 1 are shifted or rotated, theprobes 1 are positioned on the corresponding pads 2. Thus, it is notnecessary to provide a large area for the TEG 20 for contact resistancemeasurement and it is possible to measure the contact resistances of theprobes 1.

While the probes 1 are arranged on the corresponding pads 1, the pads 2may be the pads of the TEG 20 for contact resistance measurement or thepads for device electric characteristic evaluation. The pads may bedummy pads. Because the probes 1 can easily contact the pads byarranging the pads on the positions corresponding to the probes 1, apossibility that an influence is given to the precision of the probe 1when the probes 1 contact another part other than the pad on the wafer,e.g., a passivation insulating film to protect a semiconductor circuitand so on can be excluded, and a suitable embodiment can be realized.

Various layouts of the pads (arrangement positions, the number of pads2, the number of patterns, and so on) would be considered depending onthe number of probes 1 to be used. Here, for convenience of thedescription, it is assumed that the TEG 20 for contact resistancemeasurement of three pads 2 connected in series is arranged every twopads. First, as shown in FIG. 10B-1, the probes 1 are made contacts andthe resistances between the pads 2 are measured.R12=Rc1+Rc2+rR23=Rc2+Rc3+rR13=Rc1+Rc3+2r

Next, as shown in FIG. 10B-2, the probes 1 are shifted for one pad 2into the left direction, and the probes are made contact and themeasurement is performed again. In this case, the direction and distanceof a shift operation are dependent on the positions of the probes 1 atthe start and the layout of the pads 2. At this time, strictly, thecontact resistances Rc2 and Rc3 would be different in the first contactand the second contact. However, the difference in the contactresistance between the first contact and the second contact can beneglected in practice, when the difference is less than 0.1Ω. In thisexample, it is assumed that the contact resistances Rc2 and Rc3 areidentical between the first contact and the second contact.R34=Rc3+Rc4+rR24=Rc2+Rc4+2r

From the measurement through the second contact shown in FIG. 10B-2, thecontact resistances Rc1, Rc2, Rc3, and Rc4 are calculated as follows.Rc1=(2R12−R23+R34−R24)/2Rc2=(12+R23−R13)/2Rc3=(R23+R34−R24)/2Rc4=(2R34−R23+R12−R13)/2

The contact resistances Rc5 to Rcn are also measured in the same way.

When the TEG 20 for contact resistance measurement of three pads 2connected in series is arranged between two single pads, the contactresistances of all of the n probes 1 can be measured through twicecontact and measurement. Depending on the number of probes 1 of theprobe unit to be used and the arrangement position, number ofarrangements of the TEG 20 for contact resistance measurement of threepads 2 connected in series, the condition of the total number of pads,including the TEGs 20 for contact resistance measurement, the number oftimes of the contact, a shift amount and rotation is determined.

Fifth Embodiment

Referring to FIGS. 11A and 11B, in the probe unit of 24 probes 1, amethod of measuring the contact resistance of each probe 1 with the TEG20 for contact resistance measurement of three pads 2 connected inseries as shown in the fourth embodiment will be described. In thisembodiment, the TEG 20 for contact resistance measurement of three pads2 connected in series is arranged on two positions in a central area ofa TEG 4 of 38 pads.

An upper portion of FIG. 11A shows the arrangement of the pads. The twoTEGs 20 for contact resistance measurement of three pads 2 connectedseries are arranged in the pad positions 15-17, and 23-25 of the TEG 4.A lower portion of FIG. 11A shows the position of probe unit 5 to theTEG 4. The uppermost line shows the position of the probe unit 5 in thefirst contact. Subsequently, the second line, the third line, . . . showthe positions of the probe unit 5 in the second contact, the thirdcontact, . . . , respectively. A circle in a box indicates the contactof the probe 1 with any of the three pads 2 of the TEG 20 for contactresistance measurement. Through contact of eight times, it is possibleto measure the contact resistances of all the 24 probes 1. FIG. 11Bshows another example in which the position of the TEG 20 for contactresistance measurement of the three pads 2 connected in series isdifferent. In this case, the contact resistances of all the 24 probes 1can be measured through the contact of nine times.

Sixth Embodiment

FIG. 12A shows a pad 7 for resistance measurement of a linear shapewiring line pattern having a width of a pad size. Even if such a pad 7for resistance measurement is used, it is possible to measure thecontact resistances. Supposing that the film thickness of the wiringline pattern is uniform and sufficiently thin, that the n probes 1 arearranged in approximately even intervals, and that errors between theintervals are small, the resistances between the contact points or nodesof the probes 1 with the pad 7 are a constant value of r. Therefore, theresistances are equivalent to those of a pattern shown in FIG. 12B, thatis, the case of the TEG 20 for contact resistance measurement shown inFIG. 7A. Thus, the measuring method described with reference to FIG. 7Acan be applied.

Seventh Embodiment

FIG. 13 shows a pad 8 for resistance measurement which is a large areawiring line pattern. The wide area of semiconductor wafer 9 is coveredwith a conductive film and this conductive film is used as a pad 8 forresistance measurement. When a wafer on which a wiring line material ofa low resistance is formed is used, the contact resistance of all the nprobes 1 can be measured for the same reason as the sixth embodiment. Ifthe probe unit of the n probes 1 (n≧3) is smaller than the size ofsemiconductor wafer 9, it is possible to measure the contact resistanceof the probe 1. In the neighborhood of the large area wiring pattern,the resistance measured between two adjacent probes 1 is strictly theresistance varies depending on a distance from the wafer end. However,an error is negligible.

Eighth Embodiment

FIG. 14 shows a layout of a product chip 10 to which the TEG 4 with theTEG 20 for contact resistance measurement is applied. As shown in FIG.14, the TEG 4 with the TEG 20 for contact resistance measurement is laidout in advance in one or more of all the product chips 10 of the wafer.After the contact resistances of the probes 1 by using the TEG 20 forcontact resistance measurement which is contained in one product chip 10based on the method of the previously mentioned embodiment, theevaluation of the product chip 10 by using the probes 1 is performed.Thus, it is possible to evaluate the product chip 10 without beinginfluenced by the contact resistances of probes 1.

Measuring the contact resistances of probes 1 in the plurality ofpositions of the wafer surface by using either of the methods in thefirst embodiment to the eighth embodiment, it is possible to determine adistribution of the contact resistance of probes 1 due to the differencein the needle pressure which is depends on the position of the wafersurface.

Ninth Embodiment

FIG. 15A shows the structure to measure the contact resistance of theprobe 1, by utilizing unused areas such as a peripheral portion of theproduct effectively. FIG. 15A shows only a part of the peripheralportion of the wafer for convenience. However, a pattern of pads forcontact resistance measurement may be arranged in advance over the wholeperipheral portion. Like FIG. 15A, By preparing the pad 7 for resistancemeasurement as a linear-shape wiring line pattern or the TEG 20 forcontact resistance measurement in the unused area such as the peripheralportion of the product on wafer 9, the contact resistances of the probes1 can be measured in the same way as in the sixth embodiment.

As the application example shown in FIG. 15B, a conductive film isformed in the unused areas such as the peripheral portion of the productat the same time as a top wiring layer and is covered with an insulatingfilm 23, and a part of the conductive film is exposed by forming windows24. By using the conductive film part as the pads 8 for resistancemeasurement, the contact resistances of the probes 1 can be measured. Asshown by this example, the insulating film 23 is formed on the uppermostconductive film in all of the pads 7 for resistance measurement as thelinear wiring line pattern, the TEG 20 for contact resistancemeasurement, and the pad 8 for resistance measurement as a large areawiring pattern, to protect those patterns. Thus, by forming the window24, the area as a node can be exposed and formed.

[Arrangement of Pad for Resistance Measurement]

Next, an embodiment of arraigning pads for resistance measurement willbe described. Actually, when TEGs in a semiconductor product should bedesigned, it is intended to produce a large number of kinds of TEGs inan area for the TEG. For this reason, it is often difficult to preparean exclusive area for the pads for resistance measurement.

Therefore, by arranging the pads for resistance measurement in the areawhere the TEGs for device electric characteristic evaluation cannot bearranged, it is possible to easily arrange the pads for resistancemeasurement as a part of the attachment TEGs of the semiconductorproduct. Such an area is an area of a lower layer pattern such as analignment pattern, especially, which is positioned on scribe lines andis formed through synthesis of the adjacent exposure fields, in the endportion of a region formed through one exposure step (to be referred toas an exposure field) when the exposure step is performed by using areduced projection type exposing apparatus.

According to the present embodiment, the area of the alignment patterncan be used which is necessarily arranged in any kind of semiconductorproduct. Therefore, it is possible to arrange the pads for resistancemeasurement as a part of the attachment TEGs in any semiconductorproduct, with no relation to the area size for the attachment TEGs.

Hereinafter, the arrangement of such a pad for resistance measurementwill be described in detail. The arrangement of the pads for resistancemeasurement can be applied to each of the previously mentioned first toninth embodiments in a range where any contradiction is not caused. Itshould be noted that the following embodiment will be described by usingthe TEG 20 for contact resistance measurement of the pads for resistancemeasurement. However, the pads may be the pads 7 for resistancemeasurement as the linear wiring line pattern, or the pad 8 forresistance measurement as the large area wiring pattern.

Tenth Embodiment

The TEG 20 for contact resistance measurement may be formed in an upperlayer of the lower layer pattern area to overlap in at least a part, ifone of the TEG 20 and the lower layer pattern area which has been formedbefore the TEG 20 does not influence to the other. As the lower layerpattern area are exemplified pattern areas associated with alignmentsuch as an alignment reference position measurement pattern and analignment error measurement pattern, pattern areas associated with stepmonitoring such as a size measurement pattern and a film thicknessmeasurement pattern, and pattern areas associated with TEGs such as TEGsfor device electric characteristics evaluation.

One example is shown in FIGS. 16A, 16B, and 16C. FIG. 16C is a crosssectional view along the line a-a′ of FIG. 16B. FIG. 16A shows a casethat the TEG 20 for contact resistance measurement is formed not tooverlap with the lower layer pattern area 25 in a height direction.

FIG. 16B shows a case that the TEG 20 for contact resistance measurementis formed to overlap with the lower layer pattern area 25 in the heightdirection. In this case, FIG. 16C shows a conductive pattern 26 which isa part of the TEG 20 for contact resistance measurement and a lowerlayer pattern 27 which is a part in the lower layer pattern area 25. Theconductive pattern 26 has a flat surface with no relation to theposition of which the upper layer of the lower layer pattern area 25overlaps. Like this example, if one of the TEG 20 for contact resistancemeasurement and the lower layer pattern area 25 which has been formedbefore the TEG 20 does not adversely influence to the other, the TEG 20for contact resistance measurement may be formed above the lower layerpattern area 25 to overlap with a part of the lower layer pattern area25. It should be noted that FIG. 16C shows an example in which thewindows 24 are formed by forming the insulating film 23 above the TEG 20for contact resistance measurement and removing the insulating film 23from areas for the pads to which the probes 1 are made contact.

As the lower layer pattern area 25 shown in FIG. 16B are exemplifiedpattern areas such as an alignment related pattern area, a step monitorrelated pattern area and a TEG related pattern area. The alignmentrelated pattern area is pattern areas used in a lithography step such asthe alignment reference position measurement pattern and the alignmenterror measurement pattern. The step monitor related pattern area ispattern areas such as the size measurement pattern, and the filmthickness measurement pattern. The TEG related pattern area is thepattern areas of the semiconductor circuit provided to perform thedevice electric characteristic evaluation.

The above-mentioned alignment related pattern includes a pattern groupformed based on the arrangement and combination of the plurality ofelement pattern. The phrase “pattern area” shows an area of the wholepattern group.

When the TEG for the contact resistance measurement is formed to overlapwith the lower layer pattern area, a case that one of them influences tothe other at least will be thought of.

(1) When the measurement of the alignment related pattern becomesimpossible, by forming the TEG above the alignment related pattern usedin a lithography process to form an opening of a passivation film on thepad, the use purpose of the lower layer pattern is not achieved.

(2) When the surface of the conductive pattern of the TEG for contactresistance measurement becomes not flat by forming above the lower layerpattern with a step so that measurement precision is degraded, the usepurpose of the TEG for contact resistance measurement is not achieved.

It is desirable to arrange the TEG for contact resistance measurement onthe position on which these adverse influences can be avoided.

As shown in FIGS. 16B and 16C, the TEG 20 for contact resistancemeasurement is suitable if the TEG 20 for contact resistance measurementis formed above the lower layer pattern area 25 which is not used afterthe TEG 20 is formed, to overlap with the lower layer pattern area 25 inthe height direction, and the conductive pattern 26 of the TEG 20 forcontact resistance measurement has a flat surface so that the surfacedoes not the adverse influence measurement precision.

Eleventh Embodiment

The TEG 20 for contact resistance measurement may be formed by usingplural times of the exposure process. By the exposure of the pluralityof number of times, a part of the TEG 20 for contact resistancemeasurement may be exposed plural times. Through this multiple exposure,the part of TEG 20 for contact resistance measurement may betransformed.

FIGS. 17A to 17F show an example. For example, FIG. 17A is a schematicdiagram showing a lower portion in the exposure field when the exposureprocess is performed by using a reduced projection type exposureapparatus. The line b-b′ shows a centerline in the scribe line area. Anupper portion of the TEG 20A for contact resistance measurement isformed on the scribe line area 30A in the exposure field lower portionadjacent to a product area 29A.

FIG. 17B is a schematic diagram showing a lower portion in the exposurefield, similar to FIG. 17A. The line b-b′ shows the centerline in thescribe line area. A lower portion of the TEG 20B for contact resistancemeasurement is formed on the scribe line area 30B in the exposure fieldupper portion adjacent to a product area 29B.

FIG. 17C shows the TEG 20 for contact resistance measurement formed whenthe sections shown in FIGS. 17A and 17B are arranged adjacently. Theline b-b′ shows the centerline in the scribe line area. In this TEG 20for contact resistance measurement, the TEG 20A for the contactresistance measurement shown in FIG. 17A is formed in the lower portionin the topside area and the TEG 20B for contact resistance measurementshown in FIG. 17B is formed the upper portion in the underside area. Thelines b-b′ of FIGS. 17 A and 17B are coincident with the line b-b′ ofFIG. 17C.

For example, FIG. 17C shows a boundary section in adjacent exposurefields when exposure is performed by using the reduced projection typeexposure apparatus while shifting a wafer at a predetermined pitchdefined based on the size of the exposure field. The scribe line area30A in the exposure field lower portion and the scribe line area 30B inthe exposure field upper portion are synthesized to form the scribe linearea 30. Also, the TEG 20A for contact resistance measurement and theTEG 20B for contact resistance measurement are synthesized to form theTEG 20 for contact resistance measurement. In this way, the TEG forcontact resistance measurement may be formed by using the exposureprocess plural times.

Through the exposure process plural times, there is a case that the TEGfor the contact resistance measurement is deformed. Hereinafter, thedeformation will be described. FIGS. 17D and 17E are detailed diagramsshowing the upper and lower portions in the exposure field by expandingparts of FIGS. 17A and 17B, respectively. Here, the line c-c′ and theline d-d′ show a centerline in the scribe line area.

In FIGS. 17A and 17B, the upper and lower portions in the exposurefields are shown to be coincide with the centerline in the scribe linearea shown by the line b-b′. However, as shown in FIGS. 17D and 17E,usually, the lower and upper portions in the exposure fields extend overby X from the center of the scribe line area shown by the line c-c′ andthe line d-d′. The lower and upper portions in the exposure fieldoverlap by 2× in the exposure fields.

This overlap is provided by the following reason. That is, when theexposure is performed by using the reduced projection type exposureapparatus in order while shifting a wafer in the predetermined pitchdefined based on the size of the exposure field, it is generallydifficult to make a boundary section of the adjacent exposure fieldscorrectly coincide. This is because of error factors such as an opticalerror of the exposure field size copied onto the wafer, a mechanicalerror when shifting the wafer, and a size error due to the deformationof the wafer. Therefore, there is a possibility that an un-exposedportion is formed in the boundary section of adjacent exposure fieldsdue to errors. The overlapping portions of the width X shown in FIGS.17D and 17E are provided for the purpose to prevent such an unexposedportion.

FIG. 17F shows the TEG 20 for contact resistance measurement when theupper and lower portions in the exposure field shown in FIGS. 17D and17E are overlapped. The line e-e′ shows the centerline of the scribeline area. The line e-e′ is almost coincident with the line c-c′ andline d-d′.

The portions by the width X extending from the center of the scribe lineareas shown by the line c-c′ and the line d-d′ overlap with each otherin the upper and lower portions in the exposure field. As a result, themultiple exposure portion with the width 2× is formed in the center ofthe scribe line area. In the TEG 20 for contact resistance measurementformed by synthesizing the TEG 20 a for contact resistance measurementand the TEG 20B for contact resistance measurement synthesized, themultiple exposure portion with the width 2× is formed.

Generally, the multiple exposure portion receives more energy in aphotoresist layer compared than a usual portion. Therefore, there is acase that a photoresist layer is transformed, depending on a conditionin a photolithography process. Deformation is immediately transferred tothe inner or outer pattern direction if the deformation of thephotoresist layer is caused in the end of the pattern, and thedeformation may be copied into a pattern on the wafer through thephotolithography. FIG. 17F shows a deformation area 31 shows the patternof a pad deformed through the multiple exposure.

On the other hand, the wiring line portion which connects a pad and apad in FIG. 17F is not deformed. For example, when a pad and aconnection wiring line are formed of a same wiring line material, thewiring line which connects a pad and a pad is not a pattern end even ifit is a multiple exposure portion. Therefore, the deformation of thephotoresist layer is deformation into a direction of film thickness sothat the photoresist layer becomes thin. Thus, it is possible to formthe photoresist layer so as for a pattern itself on the wafer not to bedeformed even if the film thickness of the photoresist layer isinfluenced. In this case, because the shape of the wiring line materialin the connection wiring line portion is not deformed, there is not aninfluence to the wiring resistance and the adverse influence is not inthe measurement precision of the TEG 20 for contact resistancemeasurement.

As shown in the eleventh embodiment, a part of the TEG 20 for contactresistance measurement may receive multiple exposures. Also, if theadverse influence is not in the measurement precision, the part of theTEG 20 may be deformed through the multiple exposures.

Twelfth Embodiment

The TEG 20 for contact resistance measurement may be formed on both ofthe scribe line areas in a horizontal direction and a verticaldirection.

FIG. 18 shows an example. Four product areas 29 are formed in oneexposure field 32. A scribe line area 30 is formed between the adjacentproduct areas 29. Such an exposure field 32 is periodically formed in aconstant pitch.

In the boundary section of the exposure field 32, the scribe line areas30 are synthesized from the adjacent exposure fields. Also, the TEG 20for contact resistance measurement is synthesized. The TEG 20 forcontact resistance measurement is formed on the scribe line areasextending in the horizontal direction and in the vertical direction.

There is a case that various types of TEGs of device electriccharacteristic evaluation are arranged in the scribe line areas in thehorizontal and vertical directions. In such a case, when both of theTEGs on the scribe line area in the horizontal direction and the TEGs onthe scribe line area in the vertical direction are used for measurementby using the probe unit of a plurality of probes, it is necessary torotate the wafer on a wafer stage by 90 degrees. Generally, theorientation of the wafer is changed by setting again. In case that thean axis of the wafer stage is inclined, the probe contact resistance isdifferent due to the difference in needle pressure, between a case ofthe measurement of the TEGs in the horizontal direction and a case ofthe measurement of the TEGs in the vertical direction after therotation. Therefore, there is a possibility to be caused an error.

To solve this problem, it is desirable to arrange at least one TEG 20for contact resistance measurement in the horizontal direction and atleast one other TEG 20 for contact resistance measurement in thevertical direction, so that the probe contact resistance can be checkedeven in any orientation of the wafer.

By combining the tenth embodiment and the eleventh embodiment, andproviding the TEG 20 for contact resistance measurement above thealignment related pattern area which is arranged in the boundary sectionof the exposure fields 32, this problem can be solved. The alignmentrelated pattern areas are always arranged in the horizontal and verticaldirections even in any semiconductor product. Therefore, the TEG 20 forcontact resistance measurement can be arranged in the horizontal andvertical directions, by using these pattern areas. Also, as shown inthis twelfth embodiment, the TEG 20 for contact resistance measurementmay be arranged on the scribe line areas in the horizontal and verticaldirections.

According to the present invention, by providing a wiring line patternor a TEG in which three or more pads are connected in series with lowresistance wiring lines on an evaluation wafer or a product wafer, acontact resistance every each probe can be measured. In a test and sortprocess of a product wafer and a device electric characteristicevaluation, the contact resistance and the state of the probe can besurely confirmed easily. As an example, in an ON current of a MOSFETwhich is conspicuously influenced due to the contact resistance can bemeasured without an error.

Also, according to the present invention, the contact resistance of eachprobe can be measured and the current of the device can be preciselymeasured.

Moreover, according to the present invention, by measuring the contactresistance of each probe, the probe can be determined. The measurementin a high precision becomes possible even if there is a contactresistance of about 10Ω, which cannot be measured in the related art.

In addition, by recording a contact resistance change of all the probesevery time of the measurement, the maintenance and management of theprobe unit become possible. Besides, the measurement in a high precisionbecomes possible in characteristic evaluation in a high temperature, anormal temperature, and a cold temperature, by measuring the contactresistance of the probe every temperature and monitoring a temperature.

Although the present invention has been described above in connectionwith several preferred embodiments thereof, it would be apparent tothose skilled in the art that those embodiments are provided solely forillustrating the present invention, and should not be relied upon toconstrue the appended claims in a limiting sense.

What is claimed is:
 1. A semiconductor device formed on onesemiconductor substrate, comprising: a semiconductor circuit formed onthe one semiconductor substrate; a first pad, a second pad and a thirdpad arranged over the semiconductor substrate without overlapping in ahorizontal plan view, wherein each of the first pad, the second pad andthe third pad electrically isolated from the semiconductor circuit; afirst wiring line connected between the first pad and the second pad;and a second wiring line connected between the second pad and the thirdpad, wherein the first wiring line has a same resistance as the secondwiring line.
 2. The semiconductor device according to claim 1, wherein adistance between the first pad and the second pad is equal to a distancebetween the second pad and the third pad.
 3. The semiconductor deviceaccording to claim 1, further comprising: a conductive film formed overa part of the semiconductor substrate; and an insulating film formedover the conductive film and having openings where the conductive filmis exposed therethrough, wherein the first pad, the second pad and thethird pad are areas of the conductive film exposed through the openingsof the insulating film, respectively.
 4. The semiconductor deviceaccording to claim 3, wherein the first wiring line and second wiringline comprise the conductive film.
 5. The semiconductor device accordingto claim 1, wherein each of the first pad, the second pad and the thirdpad is a probe region to be in contact with a probe.
 6. A semiconductorwafer comprising: a plurality of semiconductor circuit forming regionswhere a plurality of semiconductor circuits are formed, respectively; ascribe line area arranged between the plurality of semiconductor circuitforming regions; a first pad, a second pad and a third pad are arrangedin line on the scribe line area without overlapping in a horizontal planview, each of the first pad, the second pad and the third pad beingelectrically isolated from any semiconductor circuit; a first wiringline connected between the first pad and the second pad; and a secondwiring line connected between the second pad and the third pad, whereina resistance of the first wiring line is the same as that of the secondwiring line.